Cationic and amino-containing polysaccharides may be used in many ways, e.g. as paper additives, as chelating agents and flocculating agents or as conditioners for hair. In particular, chitosan, 2-amino-2-deoxycellulose, has broad possibilities for use, inter alia as acid-stable thickener in cosmetic preparations. The isolation of this natural polysaccharide, however, is a complex process which is reflected in high prices for the products. The high price to date counteracts broad use of these polysaccharides and polysaccharide derivatives.
For the prior art, some possibilities are already known for producing aminoalkyl-containing guar derivatives.
EP 0 175 113 A2 describes polysaccharide derivatives produced by reacting polysaccharides or polysaccharide derivatives with acetal-containing substances. For example, as polysaccharide derivative base, use is made of diethylaminoethylguar having a low degree of substitution (DS 0.12). No statements are made on the properties of the diethylaminoethylguar.
DE 28 40 011 describes a process for producing diethylaminoethylguar which is characterized in that the aqueous reaction phase is emulsified in a water-immiscible solvent with addition of a surfactant. The process has the disadvantage that considerable amounts of surfactant are used. The products claimed by the process have the disadvantage that they have a lower molecular weight and a substantially lower viscosity than the inventive products.
In U.S. Pat. No. 4,276,414, in Example 4 the reaction of guar with 0.04 mol of diethylaminoethyl chloride per mole of anhydrosugar in aqueous isopropanol is described. However, no statements are mentioned as to the properties of this low-substituted diethylaminoethylguar.
U.S. Pat. No. 3,498,912 describes the production of alkylaminoalkylguar for treating wastewater. Preference here is given to the reactions of guar with amines which contain epoxy or halohydrin (XCH2—CH(OH)—R) groups. They have a degree of substitution DS(N) of 0.01 to 0.5. Higher degrees of substitution are relatively difficult to achieve and are not preferred. The alkylaminoalkylguar is produced in an alcoholic solvent.
US 2001/0051143 A1 discloses cationically modified guar having a DS of 0.25 to 1.0 which is obtained by reaction in an alcoholic medium.
The previously known processes and their products, however, have some deficiencies. For instance, the known processes lead, in particular, to products which are not completely soluble and which, for a given starting viscosity, have for many applications too low a final viscosity (and correspondingly low molecular weight). A high molecular weight is of importance for many applications in which cationic polysaccharides may be used. Examples of these are wastewater clarification or hair conditioning.